The broad, long-term objective of the current research is to improve treatment outcomes for individuals with comorbid PTSD and alcohol abuse and dependence (AUD). Prior research has established that PTSD and AUD are frequently comorbid. Although combined treatments have been developed, they are complex and lengthy with mixed results as to their efficacy. Excellent treatments exist for PTSD or AUD alone, however, it has not been adequately addressed to what extent these treatments are effective in treating comorbid symptom presentations. To address this research gap, we will evaluate two widely accepted treatments for each respective disorder; Cognitive Processing Therapy (CPT) an effective PTSD treatment and Relapse Prevention (RP), a widely used effective AUD treatment. The purpose of the present application is to evaluate changes in both PTSD symptoms and alcohol use and cravings associated with CPT or RP treatment in individuals with PTSD/AUD, along with mediators and moderators of outcomes. We will build on our prior work using a daily telephone Interactive Voice Response (IVR) system to test models of self-medication and the sequence of symptom change for both primary and secondary symptom targets associated with each therapy with. The study will randomize 235 PTSD/AUD participants recruited from the VA and from the community to CPT, RP, or IVR assessment only (AO). Those in the AO condition will be re-randomized after the treatment phase to either RP or CPT. Individuals will be assessed pretreatment, immediately post-treatment, 3-, 6-, 9-, and 12-months post-treatment and will monitor symptoms daily throughout treatment. Creating a more comprehensive model of symptom change in PTSD and alcohol use with widely used selective treatments is critical in testing theories of PTSD/AUD, evaluating these treatments for use with PTSD/AUD, and implementing these therapies with PTSD/AUD patients in standard clinical practice. PUBLIC HEALTH RELEVANCE: This research uses innovative methodologies to explore the extent to which a standard PTSD or substance use therapy can be used to treat comorbid PTSD and alcohol abuse/dependence. Research findings should help us understand more about mechanisms of change during PTSD and substance use treatment. It is also hoped that the results will offer new treatment options for those with comorbid conditions, will help us improve existing treatments, and increase our ability to determine who may best respond to a specific treatment approach.